Cell cycle Flashcards
What is the length of a human cell cycle?
24 hours
How long does a cell undergo mitosis?
1 hour
What is G0?
Resting phase
What occurs to cells in G0?
-Senescent (growing old/not dividing)
-Quinescent (Out of cell cycle)
-Differentiated
What occurs in S phase?
Cell synthesis
What occurs in M phase?
Mitosis, DNA division
What is cytokinesis?
Cell splits in 2
What cells never leave G0?
Neurons
What are features of the cell cycle?
-Continuous process
-Stepwise process: Once per cycle, correct order, to completion
What is interphase?
G0, G1 and S phase combined
What is the purpose of interphase?
-Cell content is duplicated
-Transcribes genes, synthesizes proteins
What is the purpose of mitosis?
Divides genetic material into 2 halves
What is the purpose of cytokinesis?
Divides the rest of the cell contents into 2 cells
How is the cell cycle controlled?
Using checkpoints
What is monitored at checkpoints?
-Cell size
-Nutrient supply
-DNA quantity and quality
-Favourable environment
How are checkpoints regulated?
Signals from:
-Other cells
-Growth factors
What is the first checkpoint?
G1 checkpoint
What occurs at the G1 checkpoint?
-Cells can only enter S phase if environment is favourable
-Cell cycle stops if DNA is damaged
What is the second checkpoint?
S checkpoint
What occurs at the S checkpoint?
Cell cycle stops if DNA is damaged or unreplicated
What is the third checkpoint?
G2
What occurs at the G2 checkpoint?
-Cells enter M phase if environment is favourable and DNA replicated
What is the final checkpoint?
Metaphase checkpoint
What occurs at the metaphase checkpoint?
-Cells will exit M phase if all chromosomes are attached to spindles
What does a primary spermatocyte form during spermatogenesis?
2 secondary spermatocytes
What does each secondary spermatocyte form?
2 spermatozoa
What occurs when spermatids mature?
-Cytoplasm lost
-Nucleus condenses
-Acrosome forms
What nourishes developing sperm?
Sertoli cells
